Is the hCG Diet the Secret for Weight Loss? Does it Really Work?

September 24, 2017

The hCG diet was introduced in the 1950s and, since its inception, has been considered extremely controversial. Find out whether the hormone human chorionic gonadotropin is really a valid weight loss solution.

Meet the hCG diet: An extremely low-calorie diet plus a daily injection. Sound wild? It’s no wonder the diet has been surrounded by so much controversy. This extreme diet combines a very, very low caloric intake – typically 500 calories per day – with a daily hormonal injection of human chorionic gonadotropin (hCG). Many proponents claim that following the diet can result in an average weight loss of up to 1-2 lbs per day for up to 3 to 6 weeks. But the diet also comes with many risks that outweigh the potential benefits.

What is hCG diet?

The hCG diet was developed by Albert T.W. Simeons, MD, based on his obesity research and seemingly extensive experience using the hormone successfully.

hCG, or human chorionic gonadotropin, is a hormone that is produced by the placenta during pregnancy—the same hormone that is used as a marker in home pregnancy tests. Its function, at least in part, is to support fetal development by assuring that energy is maximally mobilized so that it is available to the growing fetus. It seems to do this by affecting the structures of the diencephalon, a part of the primitive brain that controls automatic functions in the body. Fat metabolism and storage is one of its main functions.

One of the theories of obesity is that the diencephalon can be overwhelmed by excessive stressors or imbalances (such as overeating, sedentary lifestyles, hormone imbalances, psychological, or emotional stressors, etc.,) and as a result, becomes less effective at properly using and storing fat in the body. This can lead to weight gain especially in your late 30s or early 40s, when perhaps your caloric intake remains unchanged but your level of daily exercise decreases. This dysregulation of the diencephalon may also happen as a consequence of your changing hormone levels which can start to diminish starting as early as your mid-30s.

Dr. Simeon’s hCG diet plan set out to promote weight loss by addressing these internal balances in specific ways. First, by having patients follow an ultra-low calorie diet of about 500 calories per day and secondly, by administering daily hCG hormone injections. The theory is that the hCG diet injections complement a low-calorie diet by decreasing feelings of hunger and allowing individuals to successfully maintain a low caloric intake for a longer period of time. Additionally, through mechanisms that are not yet completely understood, hCG is thought to make abnormal fat, the type that accumulates in the abdomen (especially in men) and hips (especially in women), more accessible and usable to the body—the primary reason why it is produced during pregnancy.

In this way, hCG acts as a key that unlocks access to energy in otherwise inaccessible fat stores and therefore provides additional energy to a growing fetus; or, in the case of an hCG dieter, allows the individual to access and burn their abnormal fat by boosting their metabolism. The diet works by having the body run on this now accessible energy (anywhere from 1400-7000 calories per day) wherein it is burning off what is otherwise stagnant and persistent body fat while simultaneously preserving normal and structural fat as well as muscle.

The diet is generally divided into three phases described as the loading phase, weight loss phase, and maintenance phase. The loading phase marks the initiation of receiving hCG injections and as the name suggests includes loading up the diet for two days with a high-fat,high calorie intake. The weight loss phase includes the combination of the notorious low 500-calorie diet with the hCG injections and typically lasts for a period of 3-6 weeks depending on the amount of weight loss looking to be experienced. During this phase, dieters are encouraged to eat only two meals per day which should include a lean protein , non-starchy vegetables, and a carbohydrate portion such as bread or fruit. In general, it’s recommended to avoid calorie-rich fatty foods like butter and oils and limit sugar.

Lastly, the maintenance phase signifies the transition off of the hCG hormone and a gradual return to a more sustainable, higher-calorie diet with dieters continuing to avoid high starch and sugar foods for three weeks as intake increases.

Does the hCG diet plan actually work?

While the proposed mechanism for the hCG diet may sound great in theory, multiple studies have concluded that the weight loss achieved by an hCG diet plan is likely is due to the ultra-low-calorie diet rather than the injection of the hCG hormone itself . Studies comparing the effects of those following hCG diet with those following a calorie-restricted diet produced identical amounts of weight loss in each group. Participants being given the hCG hormone also did not report a significant reduction in hunger.

Although the effects of the hCG diet were supported by Dr. Simeons’ original documented experiments and treatments in addition to a randomized double blinded study by Asher and Harper on 40 subjects in 1973, replication of these results in larger studies in more recent years have continued to fail . As it currently stands, the scientific evidence stacks strongly against the hCG diet as an effective means for weight loss.

Risks, downsides, and side effects of the hCG diet

Despite any potential perceived benefits, injection of hormones into the body and an ultra-low-calorie diet is full of potential risks and side effects. Studies report concerns with the hCG diet causing unwanted side effects such as fatigue , irritability, restlessness, depression, fluid retention, swelling, and more concerning problems such as blood clots and cancer.

Low calorie diets can also severely stre ss the body and are likely to worsen an already sluggish metabolism. This ca n often result in the loss of muscle mass rather than fat loss and promote muscle and joint pain.

As for the hCG hormone, only small studies have been done so far on the efficacy of using hCG for weight loss. Currently, hCG is approved as one part of a fertility treatment for women , so that the body can mimic the state of pregnancy and for men, the only time hCG is naturally high in their bodies is when they have cancer .


As physicians dedicated to working with the best science available, at Parsley Health we do not typically or routinely endorse or suggest the use of hCG along with very low calorie diets because of the low level of evidence in support of its safe and effective use.

Instead, our focus at Parsley Health is supporting members through their weight loss journey by recommending a more comprehensive, holistic weight management program which includes a whole food based nutrition plan, stress reduction techniques, regular exercise, and adequate nightly sleep goals. While an hCG diet might produce immediate short-term weight loss effects, the lack of sustainability for this type of eating plan and potential for negative side effects make it a risky and likely unsuccessful strategy for obtaining a stable and healthy weight over the long-term.

If you are seriously considering the hCG diet, please know this type of extreme diet should only be used as prescribed, under physician supervision, and with a plan that includes specific, individual nutritional prescriptions to assure better safety and efficacy.

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